Others have given good suggestions on how to actually boot the machine.

For future reference, if you, for some reason, do this again, (or if you actually DO want to swap the two /usr hierarchies... if you add /usr-cpy/bin to your path, you should still have access to all of your utilities...

This won't necessarily avoid trouble -- just because the temporary binaries directory is in your path doesn't mean the various background daemons that depend on it won't fail horribly...
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Gordon DavissonAug 17 '10 at 16:24